Use of products containing the chemical methylene chloride in bathrooms has been linked with 13 deaths in the U.S. over an 11-year period. (Robert M. Stenhouse/Associated Press)

Methylene chloride, a chemical commonly found in furniture paint strippers and widely used in Canada despite it being considered "probably carcinogenic to humans," has been linked to the deaths of 13 workers refinishing bathtubs in the United States.

The U.S. Centers for Disease Control and Prevention (CDC) said Friday that research that began in Michigan, following the 2010 death of a bathtub refinisher who used the chemical marketed for use in aircraft maintenance, led to a study of the 13 deaths that occurred between 2000 and 2011.

'To use products containing methylene chloride safely, work areas must be well-ventilated, and when levels of methylene chloride exceed recommended exposure limits, workers must use protective equipment.' —Dr. Kenneth Rosenman, Michigan State University researcher

The finding has prompted the Atlanta-based CDC to warn worker safety and public health agencies, manufacturers and trade groups to "communicate the extreme hazards" of the use of the chemical — also known as dichloromethane — to employers, workers and the public.

It marks the first time in the U.S. that methylene chloride has been tied to refinishing bathtubs, the CDC says in a report.

"Each death occurred in a residential bathroom with inadequate ventilation," the report says. "Protective equipment, including a respirator, either was not used or was inadequate to protect against methylene chloride vapour, which has been recognized as potentially fatal to furniture strippers and factory workers, but has not been reported previously as a cause of death among bathtub refinishers."

Tips to reduce use of dichloromethane-based products/emissions:

  • Evaluate non-dichloromethane-based stripping alternatives, or paint strippers with lower dichloromethane content.
  • Use manual stripping for easily removed coats of paint.
  • Use paint strippers that contain a wax additive.
  • Conduct paint-stripping activities with optimal temperature range, usually between 13°C and 18°C, when possible.
  • Use adequate ventilation for workers using dichloromethane-based paint strippers, but don't make ventilation excessive because it can increase solvent emissions.

Source: Environment Canada

The report's co-author, Dr. Kenneth Rosenman, in the division of occupational and environmental medicine at Michigan State University, said in a statement that it's unlikely products containing the chemical can be used safely in a small bathroom, so he urges employers to consider alternative methods of bathtub stripping.

"To use products containing methylene chloride safely, work areas must be well-ventilated, and when levels of methylene chloride exceed recommended exposure limits, workers must use protective equipment," Rosenman said in his statement.   

Proper use of chemical stressed

The chemical has been at the centre of controversy in other countries, including Canada, where it was assessed as toxic under the Canadian Environmental Protection Act because of its potential to cause harm to the environment and to human health, Environment Canada says.

Canada began aggressive efforts to limit the use of methylene chloride more than a decade ago.

"Current releases of dichloromethane could be sufficient to have adverse effects on some aquatic organisms and therefore harm the environment," Environment Canada's website says. "As well, dichloromethane is classified as 'probably carcinogenic to humans,' with the principal route of human exposure to dichloromethane being inhalation."

What is methylene chloride? A highly volatile, colourless, toxic chemical that is widely used as a degreaser, process catalyst and paint remover. Products containing the chemical are applied with a brush or aerosol can.

Environment Canada notes that commercial paint stripping is one of the largest sources of dichloromethane emissions, with furniture restoration facilities accounting for 70 per cent of the commercial use and release of the chemical.

In the late 1990s, Environment Canada and Health Canada, together with industry, environmental organizations and other government departments, gathered and analyzed technical, scientific, and economic information to determine how dichloromethane emissions could be reduced in Canada.

A working committee came up with a number of recommendations to reduce emissions by as much as 20 per cent. They included developing a code of practice for commercial paint-stripping operations that aims to reduce the use of paint stripper containing dichloromethane and improving the quality of such products.

Environmental group wants warning labels

However, the code's recommendations specify use of the chemical in stripping paint from furniture, not its use in bathrooms.

Many environmental groups say not enough is being done to ban hazardous chemical products, including those containing methylene chloride, and to warn consumers against their use.


U.S. regulators require that manufacturers put warning labels on products such as paint strippers and degreasers that contain the chemical methylene chloride. (Michigan State University/Associated Press)

The Labour Environmental Alliance Society, a Canadian organization, lists methylene chloride among eight ingredients commonly found in household cleaning and home maintenance products that are of particular concern because they are "carcinogens, endocrine disrupters or known or suspected reproductive toxins."

The society notes that methylene chloride is listed as a possible human carcinogen by the International Agency for Research on Cancer, and says regulators in the U.S. compelled manufacturers to put warning labels on products containing the chemical in 1987. While the U.S. Consumer Product Safety Commission estimates that since that time, there has been a 55 per cent reduction in the number of cancers that would have been caused by these products, there are no warning label requirements in Canada for methylene chloride, the society says.

Health Canada's Workplace Hazardous Materials Information System (WHMIS), established in 1988, is Canada's national hazard communication standard, with cautionary labelling of containers of WHMIS "controlled products." WHMIS includes methylene chloride among toxic materials that can cause serious health effects by damaging the lungs, nervous system, oxygen transport in the blood and kidneys 

A call Friday by CBC News to Environment Canada seeking comment on the CDC report on bathtub refinishing deaths wasn't immediately returned.